The present invention relates to Fourier Transform Infrared (FTIR) spectrometry systems. Its essential thrust is a departure from an approximately 40-year tradition, in order to make the systems maximally adaptive to the needs of the user.
The user of a spectrometer wants its functions to be as broad, i.e., universal, as possible. In other words, the user wants flexibility: (a) flexibility in handling different types of samples, e.g. liquids, gases, powders, coated metals; (b) flexibility in illuminating the samples in various ways, e.g., reflection, transmission, multiple internal reflection; and (c) flexibility in types of information obtained.
Two prior applications assigned to the assignee of this application illustrate advanced designs of "accessories" provided for installation as sample-illuminating apparatus in conventional FTIR spectrometer systems.
Application U.S. Ser. No. 580,120, filed Feb. 14, 1984, as a continuation of application U.S. Ser. No. 291,402, filed Aug. 10, 1981, discloses a sample-illuminating accessory for spectroscopic use, in which the radiation leaving the sample holder is traveling in essentially the same direction as the radiation reaching the sample holder. This accessory is applicable both as a transmission-type apparatus in which the radiation passes through the sample, and as a multiple internal reflectance (MIR) apparatus in which the radiation enters at one end of a sample holder providing an enclosed reflecting path and is reflected repeatedly before leaving the sample holder.
Application U.S. Ser. No. 298,067, filed Aug. 31, 1981, now U.S. Pat. No. 4,473,295, issued Sept. 25, 1984, discloses a sample-illuminating accessory for spectroscopic use, in which the radiation leaving the sample holder is traveling in a direction different from the radiation reaching the sample holder because of its reflectance by the sample. The accessory is designed to function either in a diffuse reflectance mode or a specular reflectance mode.
Both of the prior applications identified above provide sample-illuminating accessories carefully designed to fit into a sample chamber located in the spectroscopic instrument.
Applicant has now realized that such systems are unnecessarily constraining, in terms of the options available to the user of the spectroscopic instrument. As stated above, the unnecessary constraints have existed for about 40 years. The apparent reasons for such limitations have been: (a) a tendency of instrument designers to focus primarily on their own requirements, as distinguished from those of the users; and (b) the unchallenged practice of following, in the design of FTIR spectrometer systems, the same paths which had been followed in the design of "dispersive" spectrometer systems, in which wavelength encoding has been accomplished by using a diffraction grating or a prism to spectrally disperse the radiation, which is focused at an entering slit, passes through the sample, and is then diverging as it emerges from the slit. The accessory complications caused by such focusing requirements are discussed in the "Background" portions of the identified prior applications.
Because the list of available functions for FTIR spectroscopy is long and growing, a major purpose of the present invention is to permit the user of spectroscopic systems to accomplish most or all of those spectroscopy functions with a single basic system, and to interchange such functions easily, and without loss of precision. Maximum flexibility is thus provided for the user, who may be a forensic analyst examining microscopic samples, a biological researcher doing in vivo analysis, or a quality control manager needing to process hundreds of samples a day with minimum operator involvement.
Another major purpose of the present invention is to eliminate wasted time. Heretofore, most FTIR spectrometers have made time saving improvements primarily in data acquisition. The present invention recognizes and deals with the remaining time factors, including the time required between insertion of successive samples, and the time required for converting from one sample-illuminating mode to another.